Blood supplies have been depleted to emergency levels for the Red Cross in New York, leading to an "urgent call for blood donors."

The organization said on Monday that donations lagged during Fourth of July holiday week, prompting the supply status to change from "critical" to "emergency." In a critical situation, the agency is taking in about as much through donations as it is sending out to health care providers. But emergency status is declared with the amount going out is greater than donations, resulting in a depletion of reserves, according to The Red Cross.

A confluence of factors led to the shortage, according to Red Cross spokesperson Patty Corvaia, who warned of a worsening supply situation on Friday. People are less likely to donate blood in the summer months, and particularly when on vacation, as was the case during the holiday week, she said.

Also, 20 percent of all donations come from high school and college students, who are out of session over the summer and are also less likely to donate in their home towns, she said.

The latest declaration from the Red Cross said that as many as 15,000 fewer donations than needed were received last week nationwide.

"Each and every day, individuals across the country depend on blood and platelet donations for lifesaving treatments and emergency care, so it's critical that people donate now to meet these needs," said Cliff Numark, senior vice president for Red Cross Blood Services.

In the Capital Region in particular, the perennial summer deficit is worse this year.

"Last year for the same time period, we had in the region a deficit of approximately 200 units," Corvaia said Monday. "This year, it's about 3,000."

Each donor usually donates one unit of blood, which is then split into red blood cells, platelets, and plasma that can go to multiple patients.

The release from the Red Cross added that type O blood donors are in the highest demand because it is often the first to be depleted from reserves. Type O blood is the universal blood type, making it coveted by hospitals and emergency room personnel when there may not be enough time to determine what blood type a patient is.

To schedule a donation, call 1-800 RED CROSS (1-800-733-2767) or enter your ZIP code on the website, www.redcross.org, to find the nearest and soonest blood drive.